Dryer control using thermally magnetizable elements



Aug. 31, 1965 D. w. SCOFIELD DRYER CONTROL USING THERMALLY MAGNETIZABLE ELEMENTS Filed Sept. '7, 1962 Y E o 7 Ma/o/ INVENTOR. 00/1071!) M 560/7510 United States Patent M 3,203,107 DRYER CONTRUL USING THERMALLY MAGNETHZAELE ELEMENTS Donahl W. Scotieid, G-lenside, Pm, assiguor to ihilco Corporation, Philadelphia, Pa, a corporation of Delaware Filed Sept, 7, 1962, gar. No. 222,065 6 Ciaims. (Cl. 34-48} This invention relates to apparatus wherein materials are treated by mechanically rolling or tumbling them while traversing them with a current of a drying medium such as heated or dehumidi-fied air. The invention relates particularly to means for measuring the progress of such treatment and drying in the rolling, tumbling or irregularly moving materials. The measurement is needed for properly controlling the application of the drying machine, for instance when treating fabrics in a home laundry as will be described herein.

Various measuring instruments and systems have been proposed and tried for such purposes; in practice, however, it is impossible to utilize certain of the measuring elements which are available in theory, as it is necessary not only to make the response very rapid, sensitive, corroot, and reliable, which by itself is diliicult, but also to do so at minimum cost and with minimum use of space, service facilities and the like. F or instance the well known temperature and humidity sensing devices, when installed in a rotating fabrics-tumbling container, are dependent on transmission of their response through electric slip rings and the like; this kind of transmission is undesirable in an installation which operates in the hot and humid atmosphere of a drying machine. It is too dependent on expert service and maintenance.

Various attempts were heretofore made to determine the effects of drying operations in a more satisfactory way, especially by indirect methods utilizing for instance measurements of temperature of the air exhausted from the tumbling drum. In relatively advanced dryer control systems presently used, reliance is placed on various subtle relationships between such exhaust air temperatures and the actual thermal conditions prevailing within the tumbling drum. However, the indications of such an exhaust system are not a direct function of the actual dryness or temperature of clothes remaining within the tumbling container; they are subject to distortion for instance :by heat retained in duct walls and the like.

For such and related reasons there has long been a recognized need for a better and a substantially direct way of determining drying conditions, without reliance on slip rings and without reliance on indirect determinations and the like.

It has occurred to me that vastly improved determination of drying conditions can be had by associating the wall of the tumbling drum with a series of elements magnetizable and demagnetizable under thermal control. Inner surface portions of such elements can be thermally coupled to the tumbling fabrics and outer surface portions can inductively control an outer, generally stationary control system. The invention has the object of providing a dryer or the like with a treatment measuring or controlling system utilizing this concept.

A preferred embodiment of the invention is illustrated in the drawing appended hereto, wherein FIGURE 1 is an elevational and partly sectionalized view of a machine constructed in accordance with this invention, and FIG- URE 2 is an electric circuit diagram of this machine.

As shown in FIGURE 1 tumbling basket or drum has a cylindrical side wall 11 which in accordance with the invention has a series of thermally controllable, magnetizable elements 12 incorporated therein. Wall 11 can be made of non-magnetic material such as aluminum,

3,2h3di37 Patented Aug. 31, 1965 although it can also be constructed of ordinary steel and other magnetically soft materials. Elements 12 are associated in high heat transfer relation with the contents of drum 19. This can be done in a variety of ways and the elements are here shown in a simple and advantageous arrangement in which they take the form of discs, each having a flat inside surface freely exposed to the interior of the drum and flush with the inside surface of wall 1 so as not to interfere with the tumbling fabrics. Each disc is shown as mounted directly in drum wall 11 and as having a fiat outside surface exposed to the exterior of the drum.

Materials suitable for these new dryer elements 12 include for instance certain chromium-modified manganese antimonides with controlled thermal transition from the so called antiferromagnetic (that is, nonmagnetizable) condition to the so called ferrimagnetic (that is, mag netizable) state. Such antimonides are made by E. I. du Pont de Nemours & Company. They are described for instance in Physical Review Letters, volume 4, page 509 s. According to the invention the transition temperature is selected to coincide with the desired ultimate fabrics temperature, to be mentioned hereinafter.

The new discs are spaced, one from the other, peripherally of drum 10. They are shown as mounted some distance in front of a perforated rear wall 13 of the drum, which wall is exposed opposite heater 14 in a heating chamber 15. Still closer to the front of the machine an annular perforated front wall 16 of the drum is provided with a front surface exposed in a duct 17 wherefrom circulating air is exhausted.

Drum 10 is conventionally mounted in front and rear bearings 18, 19 and is rotated by a suitable contact roller 2% driven by a motor 21. The resulting tumbling or rolling of fabrics within the drum is further promoted by the provision of tumbling vanes 22. The motor may drive a suitable air blower (not shown) to re-circulate air from exhaust duct 17 to heating chamber and back through the basket as described; however, an adequate air circulating effect can also, in some cases, be established by the mere use of suitably arranged tumbling vanes 22. A dryer cabinet 23 encloses and supports the aforementioned structures and gives access to the drum or basket by a door 24.

In accordance with the invention, an electromagnetic pick-up unit 25 is stationarily mounted in cabinet 23 opposite drum lit) and in line with the outer surfaces of the aforementioned discs 12 when these discs move with drum lid. The movement of the discs occurs in a circular path under the guidance of bearings 18, 19. Unit 25 faces one point or portion of this path. The pick-up unit serves to control a relay R for the control of heater 14 as is very schematically indicated in FIGURE 1.

An electrical arrangement of this pick-up unit and relay is more fully shown in FIGURE 2. It comprises a stationary normally non-magnetized iron core 26 in pickup unit 25, the poles of this core being presented toward the rotating, controlledly magnetizable elements 12 on drum iii. A winding 27 on this iron core is connected by circuit 23 with the winding 29 of a vibratory, electrically magnetizable fork 3d, and circuit 28 also includes the secondary coil of a power source transformer 31, the primary terminals of which have a -cycle potential connected thereto.

In an initial phase of normal operation, when the machine is at rest, the circuits connected with electric supply lines L L are open at a main switch 32. When this main switch is closed, motor 21 rotates dryer drum 10 and initiates the circulating of air, and heater 14 then eats the so circulated air, thereby heating fabrics F in drum 1 and beginning to dry them.

So long as the fabrics are still at low or medium temperatures, discs 12 are anti-ferromagnetic (non-magnetized and substantially non-magnetizable) and accordingly have no great effect upon the 60-cycle magnetizations received in core 26 from transformer 31. Coil 29 in control circuit 28 is then substantially inactive, leaving fork 30 at rest. As a result the drying operation, initiated by closure of main switch 32, continues.

As the mass of irregularly moving or tumbling fabrics F is gradually heated by the hot circulating air, discs 12 are also heated, both by direct contact with such air and by surface contact with air-heated fabrics. When said mass, internally of drum 10, ultimately reaches the predetermined and relatively high fabrics temperature corresponding to the desired degree of drying, substantially the same temperature is reached by disc 12, subject only to other heating or cooling effects which might be applied to these discs as such but which can be disregarded for present purposes. The discs are suitably selected for thermo-magnetic transition at this particular temperature, as noted above. They become ferrimagnetic at such time, that is, they begin eifectively to link the poles of electromagnet 26, thereby enhancing the current pulses in circuit 28. If wall 11 is made of steel or the like, wall portions surrounding the discs are also cyclically magnetized to some extent by the discs. From then on the continuing cyclic passing of discs 12 over pick-up unit 25, incident to rotation of drum 10, causes major pulses of magnetic flux to appear in core 26 and fork 30, one pulse whenever a disc passes the pole areas of core 26.

Typically, such passages occur 600 times per minute if for instance basket has an even dozen of discs 12 thereon and if it makes 50 revolutions per minute. Therefore, starting with the attainment of the predetermined maximum temperature in the fabrics themselves, and in the control discs directly contacted thereby, substantial pulses of current occur in coil 27, causing a similarly substantial alternating current 600 cycles per minute, or 10 cycles per second, in circuit 28 and fork winding 29.

Magnetizable fork 30 is tuned to approximately the same frequency, 10 cycles per second. Accordingly, vibration of the fork is excited as soon as the aforementioned significant pulses of current occur in coil 29. Such vibration cyclically closes a circuit from L through 32, 30 to a relay coil 33 and L A single full-amplitude excursion of fork 30 has this effect.

While the energization of relay coil 33, by itself, would be vibratory and transient if effected only by the 10 cycle current, a holding current is established at once. This can be done by a shunt switch 34, well known by itself, so that relay 35 is firmly energized and no longer dependent on vibrations of fork 30 as soon as inductive excitation of the control system has been initiated by the thermo-magnetic transition of discs 12 as described.

The relay includes a switch 36 through which heater 14 was thus far energized. The relay now opens this switch and holds it open and thereby de-energizes heater 14.

Thus it will be seen that the new system of discs 12 and control unit 25, 35 provides a control action substantially directly responding to the internal fabric temperatures, in the external heater-dryer system. It will also be seen that the system does so without reliance on slip rings and without reliance on temperature measurements obtained remotely from the fabrics.

A cooling operation is often desired for the fabrics in drum 10. It is therefore preferred that the tumbling of these fabrics continue for a short time after the deenergization of heater 14 which has been described above. Pursuant to such cool-off period, which may last for instance five minutes, the machine can be brought to rest by manually or automatically re-establishing the original open condition of main switch 32.

While only a single embodiment of the invention has been described, the details thereof are not to be construed as limitative of the invention. The invention contemplates such variations and modifications as come within the scope of the appended claims.

I claim:

1. In a dryer of the type wherein articles are tumbled in a hollow moving drum and are heated by application of hot air, while tumbling, the improvement which comprises: a series of normally substantially non-magnetizable bodies distributed over and secured to the hollow drum for movement with the same, said bodies consisting of material which becomes readily magnetizable at a predetermined elevated temperature thereof, a first surface of each body being arranged for intimate heat transfer relation with the articles tumbling in the drum and which articles are heated by the hot air, while another surface of each body faces a region outside the drum; and an electrical system, located in said region outside the drum, for responding reactively when said bodies become magnetizable to control the application of hot air.

2. In a dryer as described in claim 1 the feature that each body has said first surface substantially flush with the inside of the hollow drum.

3. In a dryer as described in claim 1 the feature that each body is a fiat disc inserted in the peripheral wall of the hollow drum.

4. In a dryer as described in claim 1 the feature that each body consists of chromium-modified manganese antimonide.

5. In a dryer as described in claim 1, the feature that said electrical system includes an electro-magnet stationarily mounted in said region, means for periodic energization of the electro-magnet, and sensing means for determining the moment when said bodies have become magnetizable and are magnetized by the energized electro-magnet.

6. In a dryer as described in claim 5, the feature that the sensing means comprises an electro-magnetic element, in circuit with said electro-magnet, said element being constructed and arranged to vibrate when said bodies become magnetized, and a circuit responsive to such vibration to control the application of hot air.

References Cited by the Examiner UNITED STATES PATENTS 1,948,357 2/34 Newkirk. 2,020,067 11/35 Keinath. 3,044,181 7/ 62 Berenbaum. 3,05 4,044 9/62 Shevel.

FOREIGN PATENTS 542,154 12/41 Great Britain.

OTHER REFERENCES Physical Review Letters, vol. 4, pp. 509-11 (3 pages), May 15, 1960,

NORMAN YUDKOFF, Primary Examiner. 

1. IN A DRYER OF THE TYPE WHEREIN ARTICLES ARE TUMBLED IN A HOLLOW MOVING DRUM AND ARE HEATED BY APPLICATION OF HOT AIR, WHILE TUMBLING,T HE IMPROVEMENT WHICH COMPRISES; A SERIES OF NORMALLY SUBSTANTIALLY NON-MAGNETIZABLE BODIES DISTRIBUTED OVER AND SECURED TO THE HOLLOW DRUM FOR MOVEMENT WITH THE SAME, SAID BODIES CONSISTING OF MATERIAL WHICH BECOMES READILY MAGNETIZABLE AT A PREDETERMINED ELEVATED TEMPERATURE THEREOF, A FIRST SURFACE OF EACH BODY BEING ARRANGED FOR INTIMATE HEAT TRANSFER RELATION WITH THE ARTICLES TUMBLING IN THE DRUM AND WHICH ARTICLES ARE HEATED BY THE HOT AIR, WHILE ANOTHER SURFACE OF EACH BODY FACES A REGION OUTSIDE THE DRUM; AND AN ELECTRICAL SYSTE, LOCATED IN SAID REGION OUTSIDE THE DRUM, FOR RESPONDING REACTIVELY WHEN SAID BODIES BECOME MAGNETIZABLE TO CONTROL THE APPLICATION OF HOT AIR. 